CFD study on the effect of gas temperature on the separation efficiency of square cyclones

Square cyclone was designed for Circulating Fluidized Bed (CFB) boiler technology and was found to be one of the most effective devices for cleaning high-temperature gases. However, the performance of a square cyclone under extreme operating conditions was not thoroughly studied before. The present study fills this knowledge gap by performing a comprehensive numerical simulation that uses computational fluid dynamics (CFD) technique to assess the gas temperature impact on square cyclone performance. The Unsteady Reynolds-Averaged Navier–Stokes equations combined with the Reynolds stress turbulence model (RSTM) were solved to simulate the gas flow. The Lagrangian method was used for particle trajectory analysis. The CFD simulations were implemented over various temperature ranges (from 293 to 700 K). Computational findings showed that particle separation efficiency decreased dramatically with increasing inlet gas temperature because of weaker swirling flow through the cyclone. As the inlet temperature increased, the centrifugal force decreased noticeably, resulting in a larger 50% cut size. The 50% cut size increased by about 10% as the inlet temperature rose from 293 to 700 K at 12 m/s inlet velocity.